Bipolar I and bipolar II: a dichotomy?

Bipolar disorder occurs in multiple forms and degrees of severity. A still unresolved issue is whether bipolar II disorder represents an autonomous type of bipolar disorder or a transitory condition between unipolar and bipolar I disorder. This chapter focuses on the distinctions and similarities between bipolar I and bipolar II disorders, and draws some conclusions about the validity of such a dichotomy. Family studies are useful for an understanding of the pathophysiology of bipolar disorders. In bipolar I patients the treatment aims to prevent manic relapses; consequently, lithium is the primary treatment in bipolar I patients because of its prophylactic effect on mania. On the other hand, in bipolar II patients it is very important to control and prevent depressive episodes; consequently, lamotrigine and antidepressant treatment, which have less propensity for hypomania induction, may be useful.